In Brief: Physicists Make a Tractor Beam in Water

Have you ever sat in the bathtub or swimming pool and made waves on the surface of the water with your hands to push or pull away a rubber duck? That's the basic idea behind what Australian physicists have been experimenting with in what popular media is calling "tractor beams" in water. Researchers at the Australian National University released a paper in Nature Physics describing how precise generation and manipulation of surface flows in a pool of water can force small objects to move against the direction of the resulting waves--returning to the source of the water disturbance. Computer models and tank experiments show how complicated and precise the movements have to be to get a desired result, but the researchers are hopeful that their discovery could be applicable for real-world tasks like collecting oil spills.